1. Field of the Invention
The present invention relates to a power supply circuitry for a microcomputer system.
2. Description of Background Information
In a microcomputer system including a microprocessor unit, memories, and a peripheral circuit such as a control circuit of input/output devices, it is general to apply a reset signal to the microprocessor unit shortly after the starting of the power supply. If, however, the peripheral circuit is activated during the reset operation of the microprocesor, it is very likely that the malfunction of the input/output devices will occur in accordance with erroneous command signals from the microprocessor unit.
Since the prior art power supply circuitries for the microcomputer system were generally constructed to supply the power currents of the microprocessor unit and the peripheral circuit at the same time, it was difficult to prevent the mulfunction of the microcomputer system at the starting period of the power supply. Therefore, it has been required to develop a power supply circuitry for a microcomputer system which can eliminate the above mentioned malfunciton of the microcomputer system.